One of my players enjoys experimenting with a lot of characters. He was tinkering with a sorcerer/barbarian multiclass and asked me if it would be possible to expend sorcery points while raging, especially to summon the Hound of Ill Omen from the shadow sorcerer subclass from Xanathar's Guide. Does expending sorcery points count as casting a spell in this instance?
I would say no to the spell you are quoting (which states "summon a hound of ill omen to target one creature you can see.) as this seems to go against the PHB section on "targets" for spells. Nearly all spell types or effects it must target something (odd exceptions such as teleport and sending etc) and the PHB section on spell targeting says: (emphasis mine).
To target something, you must have a clear path to it, so it can’t be behind total cover. If you place an area of effect at a point that you can’t see and an obstruction, such as a wall, is between you and that point, the point of origin comes into being on the near side of that obstruction.
since it is highly likely that scrying wouldn't have a clear path to the target (possible if you are on a flat plane with EXTREME line of site but generally speaking)
The scrying spell only notes that you can see and hear as if you were there, it does not say you have a clear path to the target (speaking as a rules-as-written) or can act as if you were there.
Other spells depend. I would say no to long range "sight" spells such as meteor swarm as they would break the need for a clear path to the sighted target. Sending would be irrelevant as you need the same criteria for scrying anyway. Teleport would also be iffy - simply seeing somewhere does not make the location "known to you" as such. I suppose that is a DM call on what they consider "known to you" (I wouldn't consider a "common" room as "known to you", but if there were identifying parts that made it "known to you" such as a window looking onto a recognised item or location then OK you draw where you want to go and teleport into that stone wall).
An episode of the WotC podcast also clears targeting up: You always need a clear path to target a creature with a spell. You don't necessarily need to be able to see them (i.e. heavy fog wont impede) but the travel path of the spell must be clear. The spell originates from the caster so the travel path from the caster to the target must have a clear travel path. Full cover stops travel path (including glass).
This change is balanced, probably still weaker than other subclasses.
1. Tempestuous magic for cantrips.
This is barely an improvement, in my estimation. This answer soundly reasons that this feature cannot be used as a functional fly speed. The proposed change just takes away the resource expenditure associated with it. It seems to me its equivalent to "+10 feet to your high jump".
To compare to other sorcerers, note the Divine Soul sorcerer's Otherworldly Wings feature:
Starting at 14th level, you can use a bonus action to manifest a pair of spectral wings from your back. While the wings are present, you have a flying speed of 30 feet. The wings last until you’re incapacitated, you die, or you dismiss them as a bonus action.
This probably isn't a good comparison as Otherworldly Wings is superior in every way (which it should be as a 14th level feature), but this change to Tempestuous Magic is very lack-luster.
2. Heart of the Storm for cantrips.
This is very similar to the evocation wizard's potent cantrip and empowered evocation abilities, but limited to a 10 foot area around you.
To compare to a sorcerer, this change basically brings it up to par with the Draconic Bloodline sorcerer's Elemental Affinity ability, but is again limited to a 10 foot area around you.
Overall, I'd say this is balanced compared to the other classes, maybe even still a little weaker. These changes give the storm sorcerer a bit more utility and a bit more damage output, something it lacked compared to the other subclasses, and it does so in a way that doesn't "step on the toes", so to speak, of the other subclasses. The way it gains thematically similar features to those other subclasses is still somewhat unique, and mechanically, isn't quite as powerful as those comparable features. I'd say this almost brings the storm sorcerer up to par with the other sorcerer subclasses.